Process for treating wood products

Abstract

The invention relates to an improved process for drying and preserving wood products. The improved process comprises the steps of first drying the wood products by submerging them in a naphthalene poor, coal tar based heat transfer medium under conditions of elevated temperature and reduced pressure. The dried wood products then are impregnated with a naphthalene rich, coal tar based wood preservative agent by submerging said dried wood products in said agent under conditions of both elevated temperature and pressure.

What is claimed is: 
     
       1. An improved process for drying and preserving wood products comprising: submerging said wood products in a heat transfer medium comprising a mixture of a minor portion of naphthalene rich, coal tar based, wood preservative agent selected from the group consisting of creosote-coal tar mixed solutions and creosote-petroleum mixed solutions and a major portion of a naphthalene poor, coal tar based, wood preservative agent prepared from the group of naphthalene rich preservative agent defined above, said wood products being submerged in said heat transfer medium in a treatment zone;   heating and maintaining said submerged wood products at elevated temperatures and under reduced pressures to remove a portion of water inherent in said wood products and provide dried wood products;   withdrawing said heat transfer medium from said treatment zone and introducing into said treatment zone a naphthalene rich preservative agent selected from the group defined above in an amount sufficient to submerge the dried wood products therein; and   heating and maintaining said submerged dried wood products at elevated temperatures and under elevated pressures to impregnate said dried wood products with said naphthalene rich preservative agent.   
     
     
       2. The improved process of claim 1 wherein said naphthalene poor, coal tar based, wood preservative agent in said heat transfer medium is prepared by heating wood products submerged in a naphthalene rich, coal tar based, wood preservative agent under reduced pressure to remove the moisture inherent therein in the form of steam, said steam effectively stripping the naphthalene from said naphthalene rich wood preservative agent. 
     
     
       3. The improved process of claim 1 wherein said minor portion of said naphthalene rich, coal tar based, wood preservative agent in said heat transfer medium ranges from about 0.5 to about 2.0 percent by volume of the total volume of said heat transfer agent in said treatment zone. 
     
     
       4. The improved process of claim 1 wherein the submerged wood products in the treatment zone are heated to and maintained at temperatures ranging from about 175° F. to about 225° F. and under reduced pressures ranging from about 20 to about 25 inches of mercury. 
     
     
       5. The improvement of claim 1 wherein the submerged dried wood products in the treatment zone are heated to and maintained at temperatures ranging from about 175° F. to about 225° F. and under elevated pressures ranging from about 115 psig to about 250 psig. 
     
     
       6. The improvement of claim 1 wherein said heat transfer medium is comprised of a minor portion of a naphthalene rich creosote-coal tar mixed solution and a major portion of naphthalene poor creosote-coal tar mixed solution.